The present invention relates to a wafer holder for positioning and holding a wafer, and a sample producing apparatus for producing a cross section sample from a wafer supported by the wafer holder.
Currently, a transmission electron microscope (TEM) is used for evaluating a defect on a wafer of a semiconductor or the like caused during manufacture. For the evaluation of the defect, the transmission electron microscope observes an extremely thin cross section sample cut from the wafer. This extremely thin cross section sample is produced by using a focusing ion beam apparatus. According to the sample production method using the focusing ion beam apparatus, a predetermined position of the wafer is etched by applying focusing ion beam thereto, and a thin piece having a thickness appropriate for the observation by the transmission electron microscope is produced as the cross section sample. Thereafter, the cross section sample is extracted from the wafer and transferred to the transmission electron microscope for the observation. The conventional type of focusing ion beam apparatus for producing the cross section sample has a wafer transfer mechanism for transferring a wafer from which a cross section sample is produced to a sample chamber and a cross section sample transfer mechanism for transferring the produced cross section sample from the sample chamber to the outside. In this structure, therefore, only the cross section sample is transferred from the sample chamber to the outside transmission electron microscope. According to this focusing ion beam apparatus, however, the entire size of the apparatus is large since two different transfer routes are included. In addition, since a sufficient space for the movements of both the wafer transfer mechanism and the cross section sample transfer mechanism is needed within the sample chamber, the size of the sample chamber itself increases. As a result, evacuation for the interior of the sample chamber deteriorates.
For overcoming these drawbacks, a sample producing apparatus including a wafer cassette on which a wafer is placed, a sample chamber containing an ion beam optical system and other components, a wafer transfer chamber, a cartridge transfer chamber, a cartridge transfer mechanism accommodated in the cartridge transfer chamber has been proposed (see, for example, JP-A-2002-365182). According to this sample producing apparatus, the cartridge transfer chamber has a cartridge station in which a cartridge for holding a cross section sample is stored. The cartridge is transferred between the cartridge station in the cartridge transfer chamber and the wafer cassette disposed in the wafer transfer chamber by the cartridge transfer mechanism. The wafer cassette is transferred between a sample stage in the sample chamber and the wafer transfer chamber. In this structure, a cross section sample produced from a wafer in the sample chamber is held by the cartridge and transferred to the wafer transfer chamber with the wafer. Then, the cross section sample is transferred from the wafer cassette to the cartridge station by the cartridge transfer mechanism. Therefore, the cross section sample can be transferred with the wafer cassette, and thus the volume of the sample chamber can be reduced.
According to the sample producing apparatus disclosed in JP-A-2002-365182, the cartridge holding the cross section sample is attached to a wafer holder together with the wafer for transfer. However, no specific means for attaching and detaching the cartridge to and from the wafer holder is shown in the reference. Even if fixing the cartridge to the wafer holder is possible, the wafer holder to which the cartridge is fixed is large-sized and heavyweight since the cartridge having a complicated mechanism has a certain weight. As a result, the size of the mechanism for transferring the wafer holder increases, and thus the entire size of the apparatus which accommodates the wafer holder and the mechanism for transferring the wafer holder increases.
The invention has been developed to solve the problems discussed above. It is an object of the invention to provide a compact and lightweight wafer holder capable of simultaneously transferring a wafer and a cross section sample produced from the wafer, and a sample producing apparatus having a small-sized entire structure and capable of simultaneously transferring the wafer and the cross section sample by using the wafer holder.